Evaluating uncertainty in predicting spatially variable representative elementary scales in fractured aquifers, with application to Turkey Creek Basin, Colorado

Evaluating uncertainty in predicting spatially variable representative elementary scales in fractured aquifers, with application to Turkey Creek Basin, Colorado

Computational limitations and sparse field data often mandate use of continuum representation for modeling hydrologic processes in large-scale fractured aquifers. Selecting appropriate element size is of primary importance because continuum approximation is not valid for all scales. The traditional...

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Bibliographic Details
Published in:Water resources research Vol. 42; no. 8; pp. W08410 - n/a
Main Authors: Wellman, T.P, Poeter, E.P
Format: Journal Article
Language:English
Published: American Geophysical Union 01-08-2006
Blackwell Publishing Ltd
Subjects:
aquifers
estimation
Fracture and flow
fractured aquifers
groundwater hydrology
hydrologic models
Hydrology
inversion
measurement
methodology
mountains
Physical Properties of Rocks
prediction
representative elementary flow
representative elementary scale
REV
Soil moisture
spatial variation
streams
uncertainty
Uncertainty assessment
Water budgets
Colorado
USA, Colorado, Denver
USA, Colorado
groundwater hydrology
representative elementary flow
fractured aquifers
REV
fracture and flow
inversion
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Summary:Computational limitations and sparse field data often mandate use of continuum representation for modeling hydrologic processes in large-scale fractured aquifers. Selecting appropriate element size is of primary importance because continuum approximation is not valid for all scales. The traditional approach is to select elements by identifying a single representative elementary scale (RES) for the region of interest. Recent advances indicate RES may be spatially variable, prompting unanswered questions regarding the ability of sparse data to spatially resolve continuum equivalents in fractured aquifers. We address this uncertainty of estimating RES using two techniques. In one technique we employ data-conditioned realizations generated by sequential Gaussian simulation. For the other we develop a new approach using conditioned random walks and nonparametric bootstrapping (CRWN). We evaluate the effectiveness of each method under three fracture densities, three data sets, and two groups of RES analysis parameters. In sum, 18 separate RES analyses are evaluated, which indicate RES magnitudes may be reasonably bounded using uncertainty analysis, even for limited data sets and complex fracture structure. In addition, we conduct a field study to estimate RES magnitudes and resulting uncertainty for Turkey Creek Basin, a crystalline fractured rock aquifer located 30 km southwest of Denver, Colorado. Analyses indicate RES does not correlate to rock type or local relief in several instances but is generally lower within incised creek valleys and higher along mountain fronts. Results of this study suggest that (1) CRWN is an effective and computationally efficient method to estimate uncertainty, (2) RES predictions are well constrained using uncertainty analysis, and (3) for aquifers such as Turkey Creek Basin, spatial variability of RES is significant and complex.
Bibliography:ark:/67375/WNG-NZXMJBTV-1
istex:B73A602BE6750B1898CE6082B3C047B5C7E2D1B2
ArticleID:2005WR004431
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ISSN:0043-1397
1944-7973
DOI:10.1029/2005WR004431